[Taxacom] Monophyly is testable? - diverted

Bob Mesibov mesibov at southcom.com.au
Thu Apr 9 05:48:44 CDT 2009

Curtis Clark wrote:

"> +1. I wonder how much of the systematics stoushes over the years have
> arisen because at the back of some participants' minds is the belief
> that there's One True Tree and that the real goal of systematics is to
> reveal it in all its (completely illusory) glory.

I don't think it is unreasonable to take as axiomatic that there is a
single evolutionary history of life on Earth (in contrast to parallel
histories, or only the illusion of history). I don't think it is
unreasonable to seek to know that history. True, it may not be entirely
(or even usefully) characterized as a tree, and it may not ever be
Knowable (with the capital "K"), but I don't think it's illusory."

[Back from the field]

I'm happy with your first two comments but not with your third. The 'it'
in your third sentence refers to the real evolutionary history of life
on earth, whereas my statement is clear in saying not that the real
history is illusory, but that a single, tree-form representation of that
history is illusory. You've disagreed with something I didn't say.

I suspect that long and scholarly articles have already been written
about what phylogenetic trees actually represent, but even a
non-specialist would be aware that trees with different contents and
meanings are mapped onto each other, grafted willy-nilly and generally
treated as somehow showing the overall diversification of "life". (See
also Richard's Zander comment on taxon trees in a parallel thread.)

With each mapping and grafting the content is reduced, until you're left
with a branching diagram whose components (nodes and connectors) can no
longer be identified with biological realities. What I find amazing is
that some biologists see erecting this reductionist abstraction as a
primary goal of biology. It's like a biblical scholar arguing that the
primary goal of studying scripture is to work out who begat whom. (And
whether you're religious or not, you'll understand how dumb that is.)

The real history of life, like any history, involves entities, events
involving those entities, dates and places. The One True Tree (when the
phylogeneticists finally get tired of building one) will be found to
contain only scattered bits and pieces of those things. It isn't
history, and it hasn't been assessed by historical methodology. How
could it be, when tree-hypotheses use up all available evidence in their
Dr Robert Mesibov
Honorary Research Associate
Queen Victoria Museum and Art Gallery
and School of Zoology, University of Tasmania
Home contact: PO Box 101, Penguin, Tasmania, Australia 7316
Ph (03) 64371195; 61 3 64371195
Webpage: http://www.qvmag.tas.gov.au/mesibov.html

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